Packers are mounted on tubular strings and have to pass through close clearances in existing tubulars to get to the location where the packer is to be deployed. In some cases the dimensional difference between the drift diameter of the existing tubular that the packer needs to pass and the set dimension is so great as to create problems in getting a reliable seal. The limits of the tubular in expansion can be reached in situations where the mandrel is expanded. Some examples of packers set by expansion can be seen in U.S. Pat. Nos. 6,959,759; 6,986,390; 7,051,805 and 7,493,945.
Some designs rely on the element to swell in the presence of well fluids such as water or hydrocarbons, such as: 7387158; 7478679; 7730940; 7681653; 7552768; 7441596; 7562704; 7661471. In some of these designs the reduction in stiffness and resulting contact pressure is offset with applied axial compressive forces triggered with the swelling as shown in U.S. Pat. No. 7,552,768 or thereafter as a result of pressure differentials such as U.S. Pat. No. 7,392,841. Swelling to make a seal is a time consuming process which can mean significant additional operator cost if the swelling has to conclude to a sealing condition before other steps can be undertaken in a well completion.
Some designs rely on axial mandrel shrinkage to apply an axial boost force to ends of a sealing element that is being radially expanded as illustrated in U.S. Pat. No. 7,431,078.
Other designs involved the use of packer cups that could be run through another tubular and then spring outwardly in the larger wellbore to obtain a seal. These designs suffered from potential damage during run in that could destroy their ability to seal. Their inherent design limited the speed that they could be run into or removed from a wellbore without swabbing the well coming out or pressurizing the formation on the trip into the well.
Some designs used tubular expansion combined with exterior rings that moved relatively to each other to extend the reach of a packer in the wellbore as illustrated in U.S. Pat. No. 7,661,473. This design also had an option for using a swelling material 44 as the sealing element. The expansion enhancing mechanism went the length of the seal element and due to the ramp structure it employed to enlarge wound up adding to the initial dimension while providing only a limited amount of enhancement in the radial direction to the underlying mechanical expansion of the mandrel.
US Publication 20050000697 illustrates a technique of corrugating pipe downhole to make it more flexible for subsequent expansion. US Publication 2010 0314130 illustrates using internal spacers and driving a swage through them to expand a seal into a wellbore wall.
What is needed and provided by the present invention, among other features, is the ability to parlay the expansion force of the mandrel into a rotational movement of fingers attached to a ring. The fingers bend outwardly to move the sealing element toward a wellbore wall to enhance the sealing contact. The fingers can bend independently so as to make the pushing out of the seal conform to a surrounding borehole wall that is not necessarily round and can be oval or irregular. The mandrel features an external ring that due to shrinkage of the mandrel as it is expanded winds up under the bent fingers to further hold out the fingers against the sealing element to maintain the seal. The ring and finger structure permits fluid to get under an end of the sealing element and to further aid in pushing the element against the borehole wall which can be open hole. Another ring from the mandrel exterior extends into the element to retain it against sliding force from pressure differentials. Various options are possible such as orienting the rings with fingers in mirror image orientations to enhance seal against differential pressures from above or below the set seal. The ring itself can be an extrusion barrier and as another option the seal can extend the length of the fingers and their base ring. Those skilled in the art will better appreciate the various aspects of the present invention from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.